can any body explain me when an object is under free fall, why the gravitational acceleration is taken negative? Because generally acceleration due to gravity is taken positive when it is in downward direction.
can any body explain me when an object is under free fall, why the gravitational acceleration is taken negative? Because generally acceleration due to gravity is taken positive when it is in downward direction.
The choice of coordinates are arbitrary, you can take g positive or negative depending upon how you choose the coordinates to study the motion. Let us see the following case:
Let us take upwards is positive coordinates in the motion of the vertical projectile
y = ut + ½ at2
But as acceleration is acting opposite of y axis ie. along –y axis a = -g
y = ut – ½gt2 ---1.
Now let us take the direction of earth’s gravity as positive coordinate, so movement of the projectile upwards is along –y axis, so u will be negative in this case. But g will be positive.
-y = -ut + gt2
=> y = ut - ½gt2 ---2
From 1 and 2 we see that whatever be the coordinate the final equation remains the same.
The choice of coordinates are arbitrary, you can take g positive or negative depending upon how you choose the coordinates to study the motion. Let us see the following case:
Let us take upwards is positive coordinates in the motion of the vertical projectile
y = ut + ½ at2
But as acceleration is acting opposite of y axis ie. along –y axis a = -g
y = ut – ½gt2 ---1.
Now let us take the direction of earth’s gravity as positive coordinate, so movement of the projectile upwards is along –y axis, so u will be negative in this case. But g will be positive.
-y = -ut + gt2
=> y = ut - ½gt2 ---2
From 1 and 2 we see that whatever be the coordinate the final equation remains the same.
